Helicopter rotor control mechanism



Nov. 14,, 1950 I. l. SIKORSKY ETAL HELICOPTER ROTOR common uzcnmxsu 4 Sheets-Sheet 1 Filed Oct. 31. 1945 l. l. SIKORYSKY WILLIAM E. HUNT E. F. KATZENBERGER mvgmons AGENT l. l. SIKORSKY ETAL Nov. 1950 l-IELIC'OPIER ROTOR CONTROL MECHANISM 4 Sheets-Sheet 2 Filed Oct. 31,, 1945 l. smo'nsxv WILLIAM. E. HUNT E. F. KATZENBERGER INVENTORS AGENT Nov M, 1950 i. l. SIKORSKY ETAL HELICOPTER ROTOR CONTROL MECHANISM 4 Sheets-$1190 1. 4

Filed Oct. 31. 1945 I. SIKORSKY WILLIAM E. HUNT E. F. KATZENBERGER T N E 6 A UNITED STATES PATENT OFFICE HELICOPTER ROTOR CONTROI: MECHANISM Igor I. Sikorsky, Bridgeport, William E. Hunt,

Brooklyn, and Edward F. Katzenberger, Bridgeport, Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application October 31, 1945, Serial No. 625,794

1 6 Claims (CI. Mil-160.25) z This invention relates to that type of aircraft certain dimensions and capacities of component known as helicopters which obtain their lift 61- parts will be used to explain the presently prerectly through rotors, and more particularly to an ierred embodiments involving a given capacity; improved structure and arrangement of rotor but it is to be understood that changes and equivoontr ls therefor, alent structures known to one skilled in the art The general structure and mode of operation are also contemplated and the proportions used is similar to those craft shown and described in' are only by way of example and are not to be conthe co-pending applications oi I."I. Sikorsky, U. strued in a limiting sense. v S. Appl. Ser. No. 592,862, filed May 9, 1945, and Referring now in detail to the drawings? of R. P. Alex and M. D. Bui'vid, U. S. Appl. Senna In Figfl, ti presentlyoprefrre'd' modification No. 599,920, filed June 16, 1945, the former having of the improvedhelicopter is shown in side view.

issued as Patent No. 2,517,599 Aug. 1, 1950. he helicopter omprisesa body ge e a y indi- The rotor and the pylon portion of the rotor cated by he r f r n e c r r 30 m p of controls of this invention comprise, severally, a a central portion 32 containing the engine and three-bladed rotor mounted upon a compact and appurtenances thereto to be described below, rugged driving spider; and controls including a a forward portion at which is made up in large simplified linkage of high-capacity with low pa of tra spa n mat rial 6 to pr v de a weight having an improved jack-screw type of large field of vision substantially in excess of actuator for controlling and coordinating the 180 for the occup thereof. and a tail por cyclic and collective pitch functions. 38 mounting a torque compensation rotor 40 at It is an object of the invention to provide ims extremity AS best Shown n a 1 proved rotor control means having automatic taming rotor g n y indicated y the a compensating provisions for cyclic pitch ith ter 42 is mounted above the central portion 32 respect to collective pitch changing movement, of the helicopter u n a d v af a d th and ice versa, hub thereof may have its operating parts covered Another obje t is t prgvide ompensatin by a streamlined protecting bonnet.

means for total pitch reducing moments which Landing gear Wheels 6 are paced at the sides are inherent in some blade t t of the forward part of the central portion 32 and These and other obj ts will be either obvious at third wheel 48 is mounted on the rear portion or pointed out in the following specification and thereofclaimg Rotor blades 59 of the rotor 42 have a length of In t drawings; substantially 24 feet measured from the shaft 44 Fig. 1 is an inboard profile longitudinal section and each has an area f substantially 3 /3 squar t parts in elevation, t parts broken away feet, there being three to make a total of substanand parts omitted to show the interior arranget1any 115 q re feet. The blade is built upon a t of operating t f thelhelicopter and steel spar 52 (Fig. 3) that is secured in a root the association thereof with therotor head and Cufi 54 Provided With a p of sets of perforated the torque compensation rotor; ears 56 for mounting the same to a stub spar Fig, 2 is an e1 v tion 1' i of th rotor headv on the rotor to be described hereinafter. At the with parts broken away, parts in section and rOOt end 58 0f the blade, the airfoil section is subparts omitted to clearly show the operating parts stahtielly h n wn as NACA 0012-64 and the and principles of t ti blade tapers to substantially NACA section Fig. 3 is a plan view of the rotor head with 9-6 at the o the tap beginning at pparts broken away to show the details of-conproximately 60 per cent of the radius of the airstruction thereof; foil portion of the blade. The cord at the root.

Fig. 4 is a detail sectional view' of the portion 8 is Substantially W f t a d th p cord is of the jack-screw and jack-shaft combination co- Su s nti lly one foot. operable with the controls of the rotor head and The weight of the helicopter constructed in acwith the manual control means in the cabin of cordance with this invention i approximately the helicopter; and 3725 pounds and the useful load is substantially Fig. 5 is a diagrammatic view of the manual 11 0 po n hus giving a gross weight of subcontrol means and the jack-screw operating stantially 4825 pounds. With the area of the rotor means associated therewith and with the conblades set forth above of 115 square feet, the blade trol mechanism shown in Figs. 2, 3 and 4. loading for such weight is approximately 42 In the description of the helicopter to follow, pounds per square foot of blade, and the swept disc area being substantially 1810' square feet gives a disc loading of approximately 2.7 pounds per square foot. The engine for turning the rotor 42 and the torque compensating rotor 40 is a radial Pratt and Whitney Wasp Junior engine of approximately 450 horsepower at sea level. The mounting and connections of the engine with the parts operated thereby will be described more fully below.

Fig. 1 shows the seating and control arrangement of the helicopter which has been designed primarily for observation purposes. The forward portion 34 contains an observers seat 62 at the front and a pilots seat 64 at the rear. Each of the seats has control pedals 66 arranged for convenient operation by an occupant of the seat, a control stick 08 for controlling the directional attitude of the helicopter and a total pitch control arm I0, the operation of which will be described below in connection with the control of the craft. The tandem arrangement of the controls is most advantageous for observation type craft, but it is to be understood that the controls may be substantially identical but arranged for side-by-side seating arrangement in the same manner as in the abovementioned applications.

In Fig. 1, the landing gear including the front wheels of the helicopter is shown. The landing gear is made up of external cones I2 each of which has internal tension and compression rods, not shown, secured to structural members 80 of the foundation truss of the central portion of the helicopter. The cones 12 are provided with shock struts at their ends which may be of conventional air-oil type and which carry at their lower ends axles 04 for mounting the wheels 46. Such structure provides a light weight and relatively low drag assembly and sufllcient damping to prevent ground resonance or instability upon contacting the ground because the shock struts are extended due to gravity when the helicopter is off the ground to provide a cushioned landing.

In Fig. 1, the helicopter is shown in substantially longitudinal elevational section with certain parts broken away and certain parts left out for the purpose of clarity. The central portion 32 comprises lateral main framing members 80 and longitudinal main framing members 30 secured together by angle trusses to make up a very light weight but sturdy base supporting an engine 92 upon a mount 94 secured to the frame members 30. Vertical framing members 30 are secured to the base members and tied together by upper struts 93 and lateral ties, not shown, and support radially converging members I supporting the gear box I02 and thereby the rotor shaft 44.

The forward portion 34 of the helicopter is built of sheet metal parts forming a cantilever base structure IOI supporting framing members I04 for suporting doors and the transparent material such as plexiglas 35 completing the forward portion 34. The forward portion 34 is suitably secured to the front of the central portion and may be removable bodily therefrom so that the forward portion 34 may be replaced. The base structure IOI encloses the control connections to the control members 88, 68 and I0, supports the seat 32, and houses a heating system comprising a fuel burning heater I I0 which supplies warm air through a main duct I I2 to outlets I I4 and I I6 to the interior of the forward portion 34.

The seat 64 is supported by framing members 05. Instruments I are mounted adjacent a side wall of the forward portion 34 in view of the oocupant of the pilots seat. Fire walls I I9 separate the fuel tanks from the engine and, with the side walls, also provide a passage for the engine coolant air. A partition I2I closes off the bottom of thi passage so that the air may pass out'of openings at the sides of the craft. A fire wall I I8, preferably made Of stainless steel, or the like, separates the forward portion 34 from the central portion 32 so that in the event of fire in the cen-- tral portion the forward occupants portion will be removed from immediate danger, and also provides an insulating wall between the forward and central portions for blocking excessive heat transfer tendencies between such portions.

The tail portion 38 is secured to the central portion 32 by trusses I22, and covering I24 of the central portion is faired into the tail portion to provide a streamlined structure. A shock strut I26 is mounted between the tail portion and the tail wheel 48. The tail portion 38 extends rearwardly to an extent sufllcient to mount the tail rotor 40 outside of the disc swept by the main rotor 32. The tail portion 38 is built as a substantially round sectioned cone tapering towards the rear. The tail portion is of semimonocoque construction comprising a stressed skin I30 supported radially by suitably spaced rings which may be joined by longitudinal stringers. A tail rotor drive shaft I36 is housed within a substantially semi-circular longitudinally extending cover I38 provided with bearings secured in rubber or other resilient damping material and held in place by brackets secured through the skin I30 to the rings. The drive shaft I36 is driven by suitable gearing in the gear box I02 from the engine 92 and turns a generator I50 for supplying electrical power for users thereof in the helicopter. The tail rotor 40 for compensating torque is of the variable pitch type, the pitch being controlled by the pedals 66 in the cockpit to change the thrust of the rotor 40. The pitch change mechanism may be of any known type but is preferably of that type shown in the patent to I. I. Sikorsky, No.

' 2,318,259, except that the pitch is changed by a jack-screw rather than by a bell crank and the control cables rotate a drum to turn the screw.

The construction of the blades of the tall rotor 40 comprising a spar I5I built 'of laminated plywood supporting solid ribs I53 that support a plywood cover I55, which cover is also secured to the spar I5I. A trailing edge tie strip I5! is secured to the cover I55, the ribs I53 and to the spar I5I at its end. The spar I5I is bolted to a pivot support bracket. Such blade construction is easily fabricated, of light weight, and has good aerodynamic characteristics.

The engine 92 is surrounded by a cowling I52 which directs air from the passage named above through the fan part of a combined centrifugal clutch and fan I54 down past the engine cylinders and out of suitable side outlets in part, and in part through a duct I55 surrounding an exhaust stack I53 from the engine 92. The air. thus, cools the engine and the exhaust gases to prevent overheating of the engine and to increase the efficiency of the engine by cooling exhaust gases and thus reducing exhaust back pressure operative against the pistons within the cylinders. The cooling air is introduced into the passage formed in the central portion 32 through the pylon at the forward part thereof wherein adjustable shutters I50 are mounted and controlled by thermostatic means, not shown, adjacent the engine; or by a manual control arm and linkage shown diagrammatically at I62. The control construction may be of any conventional type and the details thereof form no particular part of this invention.

The engine 92 turns a drive shaft I62 which turns a high speed gear of the gearing within the gear box I02 to turn the tail rotor drive shaft I36 and the main rotor drive shaft 44 to which the main rotor blades 60 are attached by the hub; A free wheel, or overrunning clutch may be within the housing so that the main rotor may autorotate and turn the tail rotor.

The engine 92 is supplied with fuel from a pair of fuel tanks I64 mounted in the center portion 32 of the helicopter and supported by members 96. The tanks I64 are mounted fore and aft of the engine 92 and the center of gravity of the helicopter is controlled by selectively drawing off fuel from one or the other of the tanks to reduce the weight of fuel therein to shift the center of gravity away from the tank from which fuel is being withdrawn.

In Figs. 2 and 3, the connection of the blade spars 54' with the drive shaft 44, and the control connections to the rotor head are shown. The drive shaft 44 extends upwardly from the upper part of the gear box I02 in which it is mounted on a thrust bearing, not shown, to assume lift loads and on a radial bearing to assume horizontal loads and is secured to a spider I12 which includes radially extending spindles I 14 having substantially horizontal axes spaced 120 degrees from each other to accommodate the mountings for three rotor blades. Each spindle I14 is adapted to receive needle bearings I16 which mate with internal shoulders I18 of a flapping link I80. Passages I8I supply lubricant to the needle bearings I16 and a grease fitting I84 is provided for filling the bearings. The flapping link I80 is secured on the spindle I 14 by a lock nut and thrust bearing assembly I85. Each flapping link I 80 has a vertical hinge I82 at its outermost end which mounts a journal 204 which in turn mounts a stub spar I83 that is provided at its end with perforated ears I86 that mate with ears 56 on the cuff 54 containing the blade spar 52 and receive a pair of taper pins I81 for securing the two together. With such arrangement of the flapping link I80, the blades connected thereto can flap upwardly around the spindles I 14 on the spider I12 and rotate backward and forward around the vertical hinge I82 to relieve stresses during flight. This latter action is restrained by dampers I90, each comprising a cylinder I92 containing a piston I94 carried upon a piston rod I96 which is pivoted at one of its ends on a pin I98 in the flapping link I80 (Fig. 3). A yoke 200 is secured to the cylinder I92 and to the journal 204 so that the cylinder is constrained to move with the stub spar I83 as it, in turn, moves with the blade to which it is attached. The cylinder I92 and piston I94 can move with respect to each other, and the liquid contained within the damper I90 will have to pass from one chamber to another through a suitable restriction, not shown, to damp such action. The limits of movement of the damper is determined by resilient stops 202 mounted upon the piston rod I96. For further details of the damper, reference may be had to the co-pending application of M. D. Buivid, Ser. No. 618,560, filed September 22, 1945.

The rotor blades 50 of this helicopter are mounted for pitch change upon the journal 204 within the stub spar I83, which two are secured together by anti-friction thrust bearings, not

shown, capable of absorbing the centrifugal loading of a blade 50 when in operation. The stub spar, the spar 52 solidly connected therewith by the cuff 54, and the connecting ears 56 and I86 are rotatable together upon the journal 204 and are turned by a rocker arm 200 secured to the stub spar I83. The rocker arm 206 extends towards the trailing edge of the blade 50 and is connected by a push-pull link 208 (Fig. 2) by pivots to a crank 2I0 mounted in a bearing 2I2 (Fig, 3) carried upon a bracket 2I3 (Fig. 2) atop the flapping link I for pivotal movement upon a crank shaft 2I6. Auniversal joint 2I4- connects the crank shaft 2I6 with a rocker shaft 2 l8. The universal joint 2I4 has its center in vertical alignment with the drag hingeor pivot I82 so that fore and aft movements of the blade 50 will not change the pitch setting of the blade. The rocker shaft 2I8 has its other end pivotally mounted in a bracket 220 supported atop the flapping link I80 at its inner end. A crank arm 222 extends laterally of the link I80 and is nonrotatably secured at its inner end to the rocker shaft 2I8. The outermost end of the arm 222 extends beyond the spindle cap and is provided with a universal pivot 224 connecting the arm 222 with a substantially vertical push-pull rod 226, which, at its lower end, is universally pivoted at 221 to an arm 228 of a control mechanism generally indicated by the reference character 230. As the rod 226 is raised by mechanism 230, the crank arm 222 will be raised to turn the rocker shaft 2I8 and the crank shaft 2I6 to lower the crank 2| 0 and the pitch change arm 206 to increase the pitch of the rotor blade attached thereto. When the rod 226 is lowered, the opposite action occurs and the pitch of the rotor blade will be decreased.

The pitch control mechanism 230 is mounted upon the drive shaft by a vertically slidable spherical bearing segment 232. A bearin 234 having a mating internal spherical surface is secured within a sleeve 236, which has secured to it the arms 228 for controlling the pitch of the rotor blades 50 as described above. A control plate 240 is rotatably secured by anti-friction bearings 242 to the sleeve 236. The plate 240 is maintained non-rotatable with respect to the gear box I02 by a scissors arrangement comprising arms 244 secured by a bracket 246 to the gear box I02 and by a universal connection 248 to the plate 240. The arms 228, sleeve 236 and the spherical bearing members 232 and 234 turn with the shaft 44. A scissors arrangement 250 is provided adjacent an arm 228 which is secured to a compression rod 252 (which rod provides a down stop 254 for the flapping link I80) and to a universal pivot 256 adjacent the arms 228 and arranged in a manner so as not to interfere with the oscillating action of the control rods 226.

Jackshafts 260, a pair of which are mounted diammetrically opposite fore and aft of the shaft 44, may be moved up and down differentially to cyclically change the pitch for fore and aft movements of the helicopter. A jackshaft 262 is arranged at the side of the shaft 44 and can be moved up and down together with the jackshafts 260 to change the total pitch of all the rotor blades, simultaneously, or moved separately to control the pitch cyclically for lateral movements of the helicopter. Upper universal pivot connections 263 (only one of which appears in Fig. 2) are in substantially the same plane as the universal pivots 221 of the push-pull rods 226 to provide precise control operation. Mechanism for raising and lowering the jackshafts 249 and 292 will be described more fully below.

with the blades 56 of this invention, the mass displacement is such that centrifugal forces acting upon the blades will create a force tending to reduce the pitch thereof, and thus cause a downward force on the jackshafts 266 and 262. Such force will attain a minimum value at substantially zero pitch, and a maximum at the highest possible pitch, with respect to the axis of rotation (the drive shaft 44) so long as this maximum angle does not exceed forty-five degrees. Normally, the rotor blades 89 operate between a minimum of about two degrees, and a maximum of about twenty degrees. The pitch reducing moment on each blade for such range may vary from substantially zero inch pounds at low pitch, to three hundred inch pounds at high pitch. Also, the different blades will exert cyclic forces as they are feathered. To balance such cyclic forces and compensate the total pitch reduction forces in the normal operating range for the blades 56, to reduce the operating forces required, mechanism for balancing forces between the several blades of the rotor and for compensating for such pitch reducing moments of the blades is provided which is shown generally at 264. A gimbal 266 (Fig. 3) is carried by a drive shaft extension 269, which extension also accommodates a hoisting ring 210 for lifting the helicopter. The gimbal 266 has arms 212 attached to its outer ring which connect by springs 214 to pivot mounting extensions 216 of the control arms 226. By such an arrangement, when one arm 224 is lowered and the others raised around the spherical segment 232, the arms 212 will be raised similarly. Thus, through the springs 214, which are normally in tension to compensate the pitch reducing moment mentioned above, the control force will be transferred through the parallelogram formed by the arms 226 and 212 and the springs 214 to equalize the control forces on all of the arms 228. Similarly, pitching forces acting on one arm in a cycle will have the force balanced in part by the parallel spring arrangement. If desired, the springs may be compression springs arranged with reversing linkage, and still perform the same function.

To further isolate vibration of the rotor head and to prevent these vibrations from being transferred in a substantial degree from the rotor head and control parts down to the manual control mechanism (to be described below) an improved jackshaft operator is provided which provides both total pitch and cyclic pitch changes, and is shown in some detail in Fig. 4. A bracket 280 may be secured to the gear housing I02 or other fixed parts of the craft, and connects to a housing 262 which supports by bearings 284 a rotatable internally threaded sleeve 296 which connects at its lower end with a sprocket 288. The jackshaft 260 (or 262) connects by a ball joint and radial and thrust bearing 290 with an externally threaded sleeve 292 that mates with the sleeve 266 and is internally splined to a shaft 221 which connects at its lower end to a sprocket 294 that is spaced by a bearing 296 from the sleeve 296. As the sprocket 288 is rotated with respect to the sprocket 294,-the threads between sleeves 266 and 292 will cause the jackshaft 266 (or 262) to be raised or lowered. If one sprocket is turned an equal extent but oppositely to the turning of the other sprocket, the jackshaft will move vertically as a function of the summation of these movements determined by the screw pitch. If the sprockets turn the same amount in the same direction, the iackshaft will remain stationary.

In Fig. 5, the operating mechanism for the jackshafts 269 and 262 is shown diagrammatically along with the other controls for eflecting manual control of the helicopter and including the control sticks 66 and total pitch arms 10. The pedals 66 control the tail rotor pitch by means of cables 260 and have no direct effect upon the control of the main rotor. when the total pitch arm 10 (only one of which is shown for purposes of clarity) is raised, a segment 292 is rotated in a clockwise direction to move a cable 364 toward the right to rotate a sprocket 206 in a clockwise direction and through a torque tube and additional sprocket 261 move a chain Ill in a clockwise direction to turn the several sprockets 286 in a direction simultaneously to raise the iackshafts 260 and 262 to thereby raise the whole control mechanism 290 and all of the control rods 226 to rotate all of the rotor blades 9 equally in a pitch increasing direction in the manner described above. As the control arm 10 is moved downwardly, the opposite rotations will obtain and a pitch decreasing motion will occur in the rotor blade control linkage.

When one or the other of the control sticks 69 is moved in the forward direction, for example, a quadrant 3H! will be rotated in a clockwise direction, a cable 3l2 will be moved toward the right and a sprocket 3 will move in a counterclockwise direction to rotate a chain 3" by means of a torque tube and additional sprocket 2H generally in a counter-clockwise direction, The chain 3l6 leads through suitable idler sprockets and the lower actuating sprockets 294 to rotate the rear jackshaft 266 in a clockwise direction and the forward jackshaft 260 in a counterclockwise direction which actions will differentially move the fore and aft parts of the tilt mechanism 230 t tilt it upward at the rearward part. Inasmuch as the blade control arms 222 (Fig. 3) lead the position of a blade 56 by substantially degrees in the direction of rotation, the tilt mechanism will cause the highest pitch of the blade to occur when the blade is substantially at a right angle to the left of the craft looking toward the front and the minimum pitch to occur diammetrically opposite in its path of r0- tation. This will cause the tip path plane of the blades 50 to tilt upwardly at the rear of the ship and downwardly at the front of the ship to provide a forward lateral component of rotor thrust to obtain translation and directional control thereof. Such action is more fully pointed out and claimed in the U. S. Patent to I. I. Sikorsky. No. 2,517,509 of August 1, 1950, to which reference may be had.

As the control stick 68 is moved to the right or to the left side of the forward part of the helicopter, a quadrant 220 will be rotated to move cables 322 differentially to rotate a quadrant 324 to move a cable 326 and rotate a sprocket 328. The sprocket 328 turns a torque tube and addi tional sprocket 229 to turn a, chain 230 connected with the lower sprocket 294 connected with the jackshaft 262 to tilt the mechanism 230 laterally of the craft to cause the tip path plane of the rotor blades to tilt in a direction corresponding to the tilt of the control stick 66.

While we have shown and described in particular detail the features of construction of one type of craft, obviously many modifications thereof will occur to those skilled in the art.

We claim:

1. In a helicopter having rotor blades mounte for universal movement in response to aerodynamic forces and to changes in the angle of incidence thereof, the combination of means for controlling the angle of incidence thereof cyclically and collectively comprising, universally tiltable and bodily movable means for controlling the angle of incidence, and manual control means including a plurality of jack screws, each having 10 two relatively rotatable threaded mating parts, and sprocket and chain actuators for said parts, said manual control means having connections with said sprocket and chain actuators for rotating corresponding parts of all of said jack screws simultaneously to actuate said movable means bodily to change the pitch of said blades collectively and having other connections for rotating and at one side of said drive shaft, each having concentric externally and internally threaded mating parts, a driving element carried by each part, means for moving said member bodily to collectively change the pitch of said blades including a manual member having an operative connection with the driving elements of like threaded parts of said jack screws, and means for tilting said tiltable member cyclically to change the pitch of said blades including manual means having operative connections with the driving elements of the other and mating parts of certain of said jack screws.

3. In a helicopter, a drive shaft, a rotor hub mounted on said drive shaft, a plurality of controllable pitch blades connected to said hub, means for changing the pitch of said blades both collectively and cyclicall including a bodily movable and tiltable member, jack screws operatively connected to said member at points fore and aft and at one side of said drive shaft, each having inner and outer concentric relatively rotatable threaded mating parts, bearing means mounting the outermost of said parts rotatably on the body of the helicopter, driving wheels carried by both said inner and outer parts, operating means connecting the driving wheels of like parts of said jack screws including a manually operable element for moving said member bodily to collectively change the pitch of said blades, and operating means connecting the driving wheels on the other parts of certain of said jack screws including a manually operable element for tilting said member to change the pitch of said blades cyclically.

4. In a helicopter, a vertically disposed drive shaft, a rotor hub mounted on the upper end of said drive shaft, a plurality of controllable pitch blades connected to said hub, means for changing the pitch of said blades both collectively and cyclically including a member bodily movable axially of said shaft and tiltable about said shaft as an axis, jack screws operatively connected to said member fore and aft and at one side of said drive shaft, each including inner and outer concentric parts having mutually engaging threads,

bearing means securing the outer part of each jack screw rotatably to the body of the helicopter, driving wheels carried by both said inner and outer parts for rotating each of the latter relative to the other, manually operative means including a total pitch control lever and a cyclic pitch control lever, operating means connecting said total pitch control lever with the wheels of corresponding parts of all of said jacks for rotating said corresponding parts relative to their mating parts to effect total pitch control, and operating means connecting said cyclic pitch control lever with the driving wheels of said mating parts of certain of said Jack screws for rotating said mating parts relative to said corresponding parts to tilt said member to eflect cyclic control.

5. In a helicopter, a vertically disposed drive shaft, a rotor hub mounted on the upper end of said drive shaft, a plurality of controllable pitch blades connected to said hub, means for changing the pitch of said blades both collectively and cyclically including a member bodily movable axially of said shaft and tiltable about said shaft as an axis, jack screws operatively connected to said member fore and aft and at one side of said drive shaft, each including inner and outer concentric parts having mutually engaging threads, bearing means securing the outer part of each jack screw rotatably to the body of the helicopter, driving wheels carried by said inner and outer parts for rotating each ofthe latter relative to the other, manually operative means including a total pitch control lever and a cyclic pitch control lever, operating means connecting said total pitch control lever with the wheels of corresponding parts of all of said jacks for rotating said corresponding parts relative to their mating parts to effect total pitch control, and operative means connecting the driving wheels of the mating parts of saidscrew jacks with said cyclic pitch control lever to effect tilting of said member, said latter connections being such as to rotate the wheels of said fore and aft jacks differentially and in opposite directions upon fore and aft movements of said cyclic pitch control lever and to rotate the wheel of the jack at one side of said drive shaft in opposite directions upon lateral movements of said lever.

6. In a helicopter, a drive shaft, a rotor hub mounted on said drive shaft, a plurality of controllable pitch blades connected to said hub, means for changing the pitch of said blades both collectively and cyclically including a bodily movable and tiltable member, a plurality of jack screws, each comprising inner and outer concentric parts having their proximate outer and inner surfaces provided with mating screw threads, means for supporting the outer parts of said jack screws rotatably on fixed structure of the helicopter, means for connecting the inner parts thereof to said member at points spaced laterally from said drive shaft, said jack screws being arranged relative to said shaft so that the inner parts thereof are connected to said member at points fore, aft and at one side of said shaft, driving means secured to the inner and outer parts respectively of the several jack screws, manually operable means having connections to the driving means on the outer parts of the several jack screws for rotating all of said outer parts simultaneouely to move said member bodily and change the pitch of said blades collectively, and other connections between said manually operable means and the drive means on the inner parts of certain of said jack screws for rotating said 11 inner parts of the selected jack screws to tilt said member and change the pitch of said blades cyclically.

IGOR I. SIKORSKY. WILLIAM E. HUNT. EDWARD F. KATZENBERGER.

REFERENCES CITED The following references are of record in the file 0! this patent: 10

UNITED STATES PATENTS Number Name Date D. 138,045 Sikorsky June 6, 1944 1,386,493 Guyot Aug. 2, 1921 15 1,599,955 Domier Sept. 14, 1926 1,651,716 Klemm Dec. 6, 1927 1,776,877 Yonkese Sept. 30, 1930 1,938,091 Wick Dec. 5,1933 1 2,002,944 Hathorn May 28, 1935 m Number Number Name Date Longren L July 2, 1935 Bennett Jan. 12, 1937 Tldd Dec. 2, 1941 Friedrich Sept. 29, 1942 Sikorsky May 4, 1943 30581 Aug. 21, 1945 Miller Mar. 5, 1946 Trice Apr. 23, 1946 Sikorsky June 18, 1946 Buivid Aug. 13, 1946 FOREIGN PATENTS Country Date Germany July 14, 1922 Switzerland Oct. 1, 1932 OTHER REFERENCES Aviation, November 1944, page 127. 

